The present invention relates to a dual speed induction motor and particularly to an induction motor having a running winding means and a starting winding means which is disconnected as the motor reaches or approaches operating speed.
The induction motor is widely employed in industrial, institutional and domestic application. Induction motors are constructed with a run winding and a start winding. A switch unit is connected in the circuit of the start winding to disconnect the start winding at a selected speed. Although centrifugal and mechanical switches have been used for many years, solid state switches devices have more recently been provided in place of the centrifugal switch. The inventors have heretofore developed solid state switches for multiple speed induction motors.
Several developments of switch systems for dual speed motors which provided a reliable winding control for a dual speed motor is disclosed in the inventors prior application for patent identified as "CAPACITOR-START INDUCTION MOTOR", Ser. No. 06/433,215, filed Oct. 7, 1982. Other prior switching systems for both signle speed and dual speed motors are disclosed in the discussion of the prior art in the above disclosure as well as in the patents cited in the file wrapper of the above application. Thus, in certain usess, different but constant speeds may be desired. Dual speed induction motors have been suggested in which first and second windings wound with different pole arrangements are selectively connected in circuit with a start winding and a centrifugal switch to permit operation of the motor at different speeds and with a single start winding unit.
The inventors prior disclosures particularly disclose improved AC induction motors having a separate run winding for each speed and a separate start winding with the run windings selectively connected to a plurality of power terminals which in turn are selectively connected to a single phase incoming power supply, and includes a speed-responsive, solid-state start switch means controlling the start winding connection and a second solid state switch means controlling one of the run winding as a switched speed winding. The switched run winding is selectively connected into the circuit and particularly operatively to its power terminal by a solid state gated run switch only in response to a power connection to a related power terminal to effect the second operational or speed mode of the motor. The non-switched run winding is connected either directly to the main supply terminals for the first operational mode and selectively in series with the speed change switch in the second operational mode. The terminology "switched" and "non-switched" is used to differentiate between the two run windings based on the special gated switch which is only present in the circuit of the one run winding to its power terminal. The separate start winding is also connected in circuit in series with a solid state switching means to a common connection or node between the two selection power terminals of the run windings. A centrifugal switch or other motor speed sensitive switch is connected in circuit of the power terminals and start winding to start the motor with the non-switched run winding. Depending upon the incoming power connection, operation of the start switch means changes the power connection to establish operation with power to the appropriate run winding and disconnection of the starting winding from the start circuit and from the power supply. The start switch means is selectively connected into the circuit to control the supplying of power to the start winding, and depending upon the power connection operates to remove the start winding while the main power connection maintains power to the non-switched run winding, or alternatively and simultaneously disconnects the non-switched winding and connects the second switched winding in circuit. In the prior system, a centrifugal or other speed responsive switch is connected in circuit with the two solid state switches to conjointly control the application of power to the two separate run windings and the separate start winding.